Picosecond Imaging Circuit Analysis (PICA) is a very large scale integrated (VLSI) chip testing and diagnostic technique developed by IBM Corporation (Armonk, N.Y.). The PICA technique captures weak, transient light pulses that are emitted by individual switching transistors. The technique can produce “movies of information” flowing through complex integrated circuit (IC) chips, such as microprocessors, memories, etc. The technique can be used to extract electrical waveforms inside the chip.
The PICA technique is described in detail in J. C. Tsang et al., “Picosecond Imaging Circuit Analysis,” IBM Journal of Research and Development, vol. 44, no. 4, July 2000, the disclosure of which is incorporated by reference herein. The technique is also described in detail in U.S. Pat. Nos. 5,940,545 and 6,172,512, the disclosures of which are incorporated by reference herein.
In the PICA technique, the emitted light can be collected from the frontside or the backside of an IC chip, although the backside collection is more convenient for testing chips that employ “flip-chip” packaging methodologies. The use of PICA as a diagnostic and characterization tool is a well-developed technology that provides precise timing information about specific logic gates.